Alright so maybe it is just me but does onboard sound affect performance or just sound better? Because honestly my speakers sound damn good through onboard sound. I am assuming it does affect performance though but seeing as how the only person I know who bought a sound card is my cousin and I have not seen him play games with it just music, I don't know how much performance it gives you over onboard.

Well, I haven't tried my onboard yet, but it supports Optical out, like the Xbox 360 does
On my X-FI, I'm using the Direct output (the three connections) and it sounds crap in comparision to the Xbox 360's optical out, prooving that Analog just doesn't cut it for good speakers anymore.

But My X-FI supports Coaxial, only with a special connection, which I'm yet to get.

But yeah, onbard sound SHOULD sound worse (More interference), and slow the computer down (has to run on CPU).